Ultrasound Angio data represents the amount of blood flowing in a scanned region of interest ("ROI"). The greater the number of reflectors in a particular section of the ROI, the larger the amplitude of the Doppler signal received from the particular section. For example, FIG. 3a illustrates the blood vessels near the edge of a kidney. The Ultrasound Angio signal generated by scanning the blood vessels across line 5--5 is illustrated in FIG. 3b, where the horizontal axis represents lateral position and the vertical axis represents the amplitude of the Angio data. As expected, the amplitude of the Angio region 8 for a larger vessel 10 is relatively large, and the Angio region 14 for smaller vessels 12 is relatively small.
In the past, blood flow displays have been produced by mapping the Angio data to a color hue. For example, in a typical image, sections with higher Angio values may be displayed with brighter colors and sections with lower Angio values may be displayed with dimmer colors.
One problem with displaying and interpreting Ultrasound Angio data in this manner is that small vessels are difficult to detect. The large vessels with high amplitude signals dominate the display, while the small vessels with lower amplitudes can fade into the background. Specifically, the large, high amplitude vessels will be displayed in the brightest colors and will therefore be easiest to see, while the smallest vessels will be dim and difficult to detect.
In light of the foregoing, it is clearly desirable to provide an apparatus and method for displaying blood flow which increases the visibility of smaller vessels. Further, it is clearly desirable to provide an apparatus and method for increasing the visibility of edges in an image illustrating blood flow.